1. Field of the Invention
This invention relates to a compact in-die tapping tool for threading holes in a sheet metal workpiece, which tool is particularly applicable to a progressive die method while advantageously eliminating the cost and inefficiency commonly associated with a secondary operation of having to move the workpiece to a drill press at a remote location at which the holes are threaded.
2. Background Art
As will be known to those skilled in the sheet metal industry, and particularly those familiar with progressive die methods, holes are initially punched in a sheet metal workpiece as one step of a progressive die method. It is then common to remove the workpiece to a (e.g. drill) press at a distant location so that the holes can be threaded as part of a secondary operation. The need for a secondary operation to thread the holes increases manufacturing time and handling requirements which correspondingly increases the cost of production.
The tapping tool of this invention may be easily located in and removed from a die that is used in a progressive die method, whereby to thread holes in a workpiece and eliminate the wasteful secondary step of having to remove the workpiece for threading at a remote location.
Tapping tools are commercially available in the sheet metal working art. However, such conventional tapping tools are generally characterized by large size, slow operation and high cost of manufacture. Consequently, such tools are not ideally suited for use in a progressive die method. One example of an efficient, relatively compact tapping tool that is adapted to be interfaced with a punch press is that described in U.S. Pat. No. 5,016,335 issued May 21, 1991. An important distinction between the patented tapping tool and the tapping tool of the present invention is the fact that the patented tool requires that a threaded shaft assembly be axially advanced towards a workpiece to thread the holes formed therein. However, the axial position of a threaded shaft assembly of the instant tapping tool is fixed, and the tap is advanced relative to the shaft assembly towards the workpiece.